The present invention relates to a method for propellant filling and sealing a container using a valve which permits filling and sealing a container with a valve which permits injection of a gas or pressurizing fluid propellant into an aerosol container and thereafter seals the pressurized container.
Pressurized, e.g. aerosol, containers must first be pressurized with a propellant such as pressurizing fluid or gas, for aerosol dispensing of a fluid product. The pressure in the container must be retained until the container is used. Propellant valves have been employed in the pressurizing of aerosol containers since the introduction of aerosol containers as consumer products, and such valves have also served to seal the container so that a useful pressure is retained in the container until the contents thereof have been virtually exhausted. A variety of such propellant filling and sealing valves have been employed.
One such propellant filling and sealing valve is disclosed in the Nicholson U.S. Pat. No. 3,522,900 issued Aug. 4, 1970. The Nicholson valve is seated in a first portion in a hole in a bottom wall of a container and, while the valve is in this position the container is pressurized. The valve is then moved to a second position which seals the container. In use, a first end of the Nicholson valve is inserted through a hole in the container into the interior of the container and propellant pressurizing fluid, e.g., a gas, is pumped into the container through grooves in the first end. The container is sealed by further inserting the Nicholson valve into the container. When further inserted, the grooves no longer communicate with the exterior of the container and a shoulder of the valve engages the inside of the container about the opening therein and a base is brought into contact with the outer surface of the wall around the hole to form a seal thereagainst.
The Nicholson valve is currently used with a container which houses an interior corregated plastic bottle.
Other sealing valves have undoubtedly been attempted. One such valve is disclosed in an August 1961 article in "Modern Packaging" entitled "The Free-Piston Aerosol". In that article, it was brought out that American Can Co. developed a special gassing and plugging unit for propellant filling and sealing of a free-piston type aerosol container. The unit contemplated inserting a cylindrical plug into a filling hole. The plug was cut from a continuous length of plug material fed through a special chuck orifice while the container remained pressurized to seal the aerosol.
Manufacturers of container valves, such a Vernay Laboratories, Inc. of Yellow Springs, Ohio, have produced a variety of valves for various purposes. One such non-analogus valve known as an umbrella check valve is employed in the non-analogus art of pressure relief mechanisms. In such environment, the umbrella check valve is used as a pressure relief valve for containers of volatile substances. The umbrella valve has a cross-section which is generally shaped like a letter "T", i.e. it has, an umbrella top, forming a "bar" of the "T" with a curved upper surface and a bulbous stem. The stem is partially inserted downward through a vent hole in a container top wall so that the bulbous portion of the stem is on the interior side of the container top wall and a flat portion of an undersurface of the "bar" of the "T" of the umbrella top of the valve seals against the outer surface of the top wall of the container. An interference fit is established between the container top wall containing the vent hole and an ungrooved circumference of the stem between the umbrella top and bulbous portion of the stem. When the container becomes pressurized to a predetermined pressure, such as by the ambient temperature heating of a liquid and a gas phase of the liquid in the container, the umbrella top is forced upward away from the upper outer surface of the container top wall by pressurized fluid channeled through a groove in the bulbous stem to vent the pressurized fluid until the over pressure condition is relieved.
The Nicholson valve and the American Can Co. plug require the use of somewhat complex machines which both insert the sealing valves in containers and pressurize the containers.
It has been found that the Nicholson valve may be readily forced to one side with a pencil to degas the container. Also, with a two step insertion procedure, sometimes the valve is inserted all the way, i.e. the two steps of the insertion are done in one step, before gas can be injected into the container. This results in wastage, since the container cannot then be filled with gas. Further, the American Can Co. plug may be removed with pliers.
The Vernay umbrella valve is used for pressure relief venting and not for facilitating pressurizing a container with a propellant and subsequently sealing the container.
Tests were made with an umbrella valve used in the non-analogus art of shock absorbers to see if it could be employed as a propellant filling and sealing valve and a number of drawbacks were discovered. During a high pressure filling operation with pressurized gas acting on the underside of the umbrella top, the bulbous portion of a stem of the valve exhibited a tendency to pass through the container bottom wall resulting in the valve being "blown" into the container. Also, the tight interference between the umbrella top, the wall of the container and the bulbous portion of the stem was such as to require relatively high filling pressures for product filling, which makes it difficult to vent trapped air when product filling.
Also, when high filling pressures are used to pressurize a free-piston aerosol container using such umbrella valve with a single gas filling channel along the stem thereof, the geometry of the umbrella top, with a right angle junction of stem and top, results in the flow of turbulent pressurizing fluid into the container in a manner that could cock the piston and contaminate a product with pressurizing fluid.
The Nicholson valve requires a first step insertion, propellant filling, and a second step insertion. The American Can Co. plug requires cutting the plug material to form the plug, filling, and then plugging with the cut length of plug material under pressure.
As will be described in greater detail hereinafter, the propellant filling and sealing valve of the present invention differs from the previously proposed propellant filling and sealing valves by providing an umbrella shaped valve which, for a three-piece container, preferably is placed onto the inner surface of a bottom wall for the container, before the bottom wall is joined to a container body to form a container, with a stem portion of the valve being inserted through a propellant filling hole in the bottom wall and with an umbrella of an umbrella sealing portion thereof being positioned adjacent a surface of the bottom wall which becomes an inner upper surface of the bottom wall when the container is assembled. For a two-piece container having an integral bottom, before pressurization, the valve is seated in a hole which can be in the integral bottom.